The present invention relates to an applied technical field of X-rays having a wavelength of about 10 .ANG. or less and, more particularly, to a crystal monochromator suitable for an X-ray lithography, an X-ray analysis and an X-ray analyzer, in which an X-ray beam is monochromatized and focused to irradiate a specimen with a high intensity.
In the prior art, in case an X-ray beam having a wavelength of about 10 .ANG. is to be monochromatized and focused to have its intensity increased so that it may be used for the X-ray analysis or the like, a crystal monochromator made of a single-crystal material such as Si or Ge has to be bent (with a radius of curvature R of several tens cm to several cm) to focus its diffracted X-ray beam, as is disclosed in "Interpretation of Some Experimental Data Concerning Bent Monochromators for Synchrotron X-ray Radiation" by A. Boeuf et al., J. Appl. Crystal, pp. 265 to 267, Vol. 11, 1978. In order to bend the crystal material such as Si or Ge, however, it is usually necessary to slice the crystal to a thickness of several mm or less and to apply a stress 3 from the two ends, as shown in FIG. 1. This necessity makes it defectively difficult to hold a constant curvature at each portion of the crystal having lattice planes 2.